The present disclosure relates to compositions and methods for treating subterranean formations.
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore and cemented into place. Thereafter, one or more treatments may be performed in the subterranean formation and/or the well bore to facilitate the production of hydrocarbons such as gas and oil from the well, such as enhanced oil recovery operations, stimulation treatments (e.g., hydraulic fracturing), and the like. For example, an enhanced oil recovery operation is a generic term for techniques for increasing the amount of crude oil that can be extracted from a hydrocarbon-producing formation (e.g., hydrocarbon reservoirs). Such operations can be particularly useful in unconventional reservoirs (e.g., shale) where the extraction of such hydrocarbons may not be facilitated by natural buoyant forces.
In some instances, enhanced oil recovery may be achieved by gas injection, foam injection, chemical injection, microbial injection, or thermal recovery (which includes cyclic or continuous steam, steam flooding, and fire flooding). In certain of these treatments, fluid is injected into the reservoir to displace or sweep the hydrocarbons out of the reservoir. In order to accomplish this more effectively, one or more surfactants or emulsifiers may be injected into the formation, among other reasons, to lower the interfacial tension between oil and water which allows stable emulsions with small drops to be formed that can be carried out of the formation with the fluid. Many variables may affect the selection of a surfactant for use in such treatments and operations, such as interfacial surface tension, wettability, compatibility with other additives (such as other additives used in acidizing treatments), and emulsification tendency.
However, the composition, porosity, and/or permeability of a subterranean formation and the composition of formation fluids may complicate these treatments. For example, in some instances, large amounts of the surfactant and/or emulsifier may become adsorbed onto rock surfaces in the formation before they can effectively dissolve and/or emulsify the oil in the formation. In these cases, large amounts of surfactant may be needed so that a sufficient amount remains in the fluid to reduce interfacial tension between the oil and water. In many cases, the composition, porosity, and/or permeability of a subterranean formation may vary in different regions thereof, which may make the effective treatment of the entire formation with one type of treatment impractical or difficult.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.